Liquid crystal display device

ABSTRACT

A liquid crystal display device includes: a TFT substrate having gate lines and data lines arranged thereon, the gate lines extending in a first direction and arranged in a second direction, the data lines extending in the second direction and arranged in the first direction; a counter substrate having a black matrix and a color filter; and liquid crystals put between the TFT substrate and the counter substrate. Columnar spacers are formed on the counter substrate. Pedestals are formed on portions of the TFT substrate, the portions corresponding to the columnar spacers. A convex portion and a concave portion are present at the top end of the columnar spacer. The pedestal is formed corresponding to the concave portion. The concave portion is opened at the ends thereof and connected to the lateral side of the columnar spacer.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.13/719,285, filed on Dec. 19, 2012, which claims priority from JapanesePatent Application No. 2011-277234 filed on Dec. 19, 2011 in theJapanese Patent Office, the entire contents of which are incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display device. Theinvention particularly relates to a liquid crystal display device takingmeasures to prevent bright spots caused by scraped dusts of an alignmentfilm.

2. Description of the Related Art

Liquid crystal display devices include: a TFT substrate having pixelelectrodes, thin film transistors (TFT), etc. formed in a matrix; acounter substrate disposed in facing relation to the TFT substrate andhaving color filters, etc. formed at positions corresponding to thepixel electrodes of the TFT substrate; and liquid crystals put betweenthe TFT substrate and the counter substrate. Images are formed bycontrolling the light transmittance of liquid crystal molecules for eachpixel.

In the liquid crystal display device, an alignment film is formed at theboundary between the counter substrate and the liquid crystal layer inthe TFT substrate, and the alignment film is subject to rubbing processor optical alignment process to put the liquid crystal molecules toinitial alignment. Then, the amount of light transmitted through theliquid crystal layer is controlled by twisting or rotating the liquidcrystal molecules by electric fields from the state of initialalignment.

Meanwhile, to control the thickness of the liquid crystal layer, it isnecessary to form spacers between the counter substrate and the TFTsubstrate. Conventionally, beads, etc. were dispersed as the spacers inthe liquid crystal layer. In recent years, however, to control the gapbetween the TFT substrate and the counter substrate more accurately,columnar spacers are formed on the counter substrate and the gap iscontrolled by the columnar spacers.

However, use of the columnar spacer additionally raises a new problem.JP-2000-122071-A, JP-2001-33790-A, and JP-2002-229040-A describe thefollowing. When the columnar spacer is formed on the TFT substrate, areservoir of the alignment film is formed at the periphery of thecolumnar spacer and the thickness of the alignment film is increasedtherein. To prevent such increase in the thickness, a concave portion isformed at the top end of the columnar spacer to retain the alignmentfilm in the concave portion thereby preventing increase in the thicknessof the alignment film at the periphery of the columnar spacer.

JP-2009-255529-A describes the configuration in which grooves areformed, for example, of a concentric shape at the top end of thecolumnar spacer and the liquid alignment film is accumulated in thegrooves to prevent scraping of the alignment film after drying. Further,the configuration is adapted to ensure the degree of freedom of the sizeof a pedestal disposed in facing relation to the columnar spacer.

JP-2007-94372-A describes the configuration in which grooves are formedat the surface of a pedestal disposed in facing relation to a columnarspacer and the area of contact between the columnar spacer and thepedestal is adjusted to shorten the recovery time after the substratehas been pressed from the outside.

SUMMARY OF THE INVENTION

For example, when a columnar spacer is disposed to a counter substrate,a pedestal is disposed to a TFT substrate at a portion facing thecolumnar spacer. The pedestal disposed to the TFT substrate serves toprevent scraping of the alignment film at a portion in contact with thecolumnar spacer, prevent displacement of the columnar spacer or adjustthe stress caused by an urging pressure, when the counter substrate ispressed, etc.

However, such effects were not obtained sufficiently in the related art.For example, in the techniques described in JP-2000-122071-A,JP-2001-33790-A, and JP-2002-229040-A, a concave portion is formed atthe top of the columnar spacer provided to the TFT substrate to preventformation of a liquid reservoir of the alignment film at the peripheryof the columnar spacer. However, this configuration results in a problemthat the alignment film formed thick in the concave portion at the topof the columnar spacer is scraped off from a portion where the columnarspacer is in contact with the counter substrate, and the scraped dustscause bright spots.

The technique described in JP-2009-25529-A results in a problem that thealignment film is formed thick in the concentric grooves formed at thetop of the columnar spacer, and the thick alignment film is peeled bythe contact with the pedestal. Further, in the configuration ofJP-2009-25529-A, no sufficient effect can be obtained for the positionaldisplacement of the columnar spacer.

In the technique described in JP-2007-94372-A, grooves are formed to apedestal. However, this involves a problem that an alignment film isformed thick in the portion of the grooves and the alignment film ispeeled off from the portion. Further, it is difficult by theconfiguration to suppress the positional displacement of the columnarspacer.

The present invention intends to prevent scraping of an alignment filmbetween a columnar spacer and a pedestal, prevent positionaldisplacement of the columnar spacer, prevent the columnar spacer fromfracture when the counter substrate is pressed, and rapidly recover theinitial state when the pressure is removed.

The present invention intends to overcome the problems described aboveand typically include the following means. That is, there is provided aliquid crystal display device including: a TFT substrate having gatelines and data lines arranged thereon, the gate lines extending in afirst direction and arranged in a second direction, the data linesextending in the second direction and arranged in the first direction; acounter substrate having a black matrix and a color filter; and liquidcrystals put between the TFT substrate and the counter substrate.Columnar spacers are formed on the counter substrate. Pedestals areformed on portions of the TFT substrate, the portions corresponding tothe columnar spacers. A convex portion and a concave portion are presentat the top end of the columnar spacer. The pedestal is formedcorresponding to the concave portion. The concave portion is opened atthe ends thereof and connected to the lateral side of the columnarspacer.

In this case, a usual state, that is, a state where pressure is notexerted on the counter substrate includes a case where the pedestal andthe concave portion of the columnar spacer are in contact with eachother and the convex portion of the columnar spacer is not in contactwith the TFT substrate, and a case where the convex portion of thecolumnar spacer is in contact with the TFT substrate and the pedestalportion and the concave portion of the columnar spacer are not incontact with each other.

Further, the convex portion and the concave portion formed to the topend of the columnar spacer can be in various shapes. Further, two ormore kinds of columnar spacers may be combined to provide apredetermined effect as a whole.

According to the invention, since the convex portion and the concaveportion are disposed to the top end of the columnar spacer, and theconcave portion is opened at the ends thereof and connected to thelateral side of the columnar spacer, the alignment film is not formedthick in the concave portion and, accordingly, scraping of the alignmentfilm caused by the contact between the columnar spacer and the pedestalcan be prevented.

Further, according to the invention, since the convex portion formed atthe top end of the columnar spacer serves as a stopper to the pedestal,positional displacement of the columnar spacer can be prevented.

Further, according to the invention, since one columnar spacer has aportion always in contact with the pedestal and a portion in contactwith the pedestal when the counter substrate is pressed, pressure can bedispersed and the counter substrate can be rapidly returned to aninitial state when the pressure is released. Further, the columnarspacer can be free from fracture when the counter substrate is pressed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a liquid crystal display device according tothe present invention;

FIG. 2 is a cross sectional view of a first embodiment;

FIG. 3 is a plan view showing a relation between a columnar spacer and apedestal of the first embodiment;

FIG. 4 is a cross sectional view showing an other example of the firstembodiment;

FIG. 5 is a plan view showing a further example of the first embodiment;

FIG. 6 is a plan view showing a relation between a first columnar spacerand a pedestal of a second embodiment;

FIG. 7 is a plan view showing a relation between a second columnarspacer and a pedestal of the second embodiment;

FIG. 8 is an example showing an arrangement of first and second columnarspacers in the second embodiment;

FIGS. 9A to 9C are other example showing an arrangement using firstcolumnar spacers and second columnar spacers in the second embodiment;

FIG. 10 is a modified example showing a relation between the shape of acolumnar spacer and a pedestal in the second embodiment;

FIG. 11 is other modified example showing a relation between the shapeof a columnar spacer and a pedestal in the second embodiment;

FIG. 12 is a cross sectional view showing a relation between a columnarspacer and a pedestal in the third embodiment;

FIG. 13 is a plan view showing a relation between a columnar spacer anda pedestal in the third embodiment;

FIG. 14 is a cross sectional view showing other example of the relationbetween a columnar spacer and a pedestal in the third embodiment;

FIG. 15 shows an example of an arrangement of columnar spacers in thethird embodiment;

FIG. 16 is a plan view showing a fourth embodiment;

FIG. 17 is a cross sectional view of the fourth embodiment;

FIG. 18 is a detailed plan view of the fourth embodiment;

FIGS. 19A and 19B show a cross sectional view of a fifth embodiment;

FIG. 20 is a plan view of a sixth embodiment;

FIG. 21 is a cross sectional view of the sixth embodiment; and

FIG. 22 is a plan view showing a problem when rubbing alignment isadopted.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be described specifically by way of preferredembodiments.

First Embodiment

FIG. 1 is a plan view of a pixel portion of a liquid crystal displaydevice to which the invention is applied. In FIG. 1, gate lines 101 areextended in a lateral direction and arranged in a longitudinaldirection. Further, data lines 111 are extended in the longitudinaldirection and arranged in the lateral direction. A pixel electrode 106is formed in a region surrounded by the gate lines 101 and the datalines 111. The pixel electrode 106 is formed as a solid plane on which anot illustrated inorganic passivation film is stacked and a counterelectrode 108 having slits 1081 is formed thereover. The counterelectrode 108 is formed in common with each of pixels.

A semiconductor layer 103 is formed over the gate line 101, and a drainelectrode 104 and a source electrode 105 are stacked over thesemiconductor layer 103. The drain electrode 104 is branched from thedata line 111, and the source electrode 105 is connected to the pixelelectrode 106. When a voltage is supplied to the pixel electrode 106 byway of the source electrode 105, electric fields are exerted on a liquidcrystal layer 300 through the slit 1081 of the counter electrode 108 torotate liquid crystal molecules and control the amount of lighttransmitted through the liquid crystal layer 300. In FIG. 1, a pedestal120 is formed over the gate line 101. A columnar spacer 210 formed onthe counter substrate 200 is in contact with the pedestal 120.

FIG. 2 is a cross sectional view along line A-A in FIG. 1. In FIG. 2,the pedestal 120 formed on a TFT substrate 100 is in contact with aconcave portion 212 at the top end of the columnar spacer 210 formed onan overcoat film 203 of a counter substrate 200. In the drawing, thegate line 101 is formed on the TFT substrate 100, and a gate insulatingfilm 102 is formed on the gate line 101. A pedestal base 130 is formedon the gate insulating film 102. The pedestal 120 is formedcorresponding to the pedestal base 130.

The semiconductor layer 103 or a metal layer is stacked in accordancewith a necessary height to the pedestal base 130. Layers that can bestacked include 150 nm of the semiconductor layer 103, 200 nm of thesource-drain electrodes 105, 104, and 70 nm of the pixel electrode 106formed with ITO (indium tin oxide), etc. Accordingly, when all of thefilms are stacked, the thickness can be about 420 nm.

An inorganic passivation film 107 comprising SiN is formed so as tocover the gate insulating film 101 and the pedestal base 130, and thecounter electrode 108 is formed on the inorganic passivation film 107.The counter electrode 108 over the gate line 101 is formed as a solidfilm. That is, the counter electrode 108 has the slits 1081 only in thepixel portion. An alignment film 109 is formed so as to cover thecounter electrode 108. The thickness of the alignment film 109 is about70 nm. In FIG. 2, a pedestal 120 in contact with the columnar spacer 210is formed corresponding to the pedestal base 130.

In FIG. 2, a black matrix 201 is formed on the counter substrate 200,and an overcoat film 203 is formed on the black matrix. The columnarspacer 210 is formed on the overcoat film 203. The columnar spacer 210is formed, for example, of an acryl resin by photolithography. A convexportion 211 and a concave portion 212 are formed at the top end of thecolumnar spacer 210. In FIG. 2, a pedestal 120 is in contact with theconcave portion 212 of the columnar spacer 210 to keep the TFT substrate100 and the counter substrate 200 at a predetermined gap. The concaveportion 212 and the convex portion 211 at the top end of the columnarspacer 210 can be formed, for example, by half-tone exposure. Analignment film 109 is formed so as to cover the overcoat film 203 andthe columnar spacer 210. Liquid crystals 300 are filled between the TFTsubstrate 100 and the counter substrate 200.

FIG. 3 is a plan view showing a relation between a columnar spacer 210and a pedestal 120 in the pedestal portion. As shown in FIG. 2, sincethe cross section of the columnar spacer 210 is trapezoidal, the baseportion of the columnar spacer 210 of a large width is referred to as alower bottom 216 and the top of the columnar spacer 210 of a small widthis referred to as an upper bottom 215. The top end of the columnarspacer 210 is not flat but the convex portion 211 and the concaveportion 212 are formed. In FIG. 3, a hatched portion is the convexportion 211 and other portion is a concave portion 212.

In FIG. 3, a concave portion 212 has a grooved shape and a groovethereof is opened at both ends. That is, the groove is connected to thelateral side of the columnar spacer 210 not by way of the convexportion. That is, the concave portion 212 is not surrounded at theentire circumference by the convex portion 211. This is greatlydifferent from the known columnar spacer. Accordingly, after thealignment film 109 is coated in a liquid state, the alignment film 109does not accumulate in the concave portion 212, that is, in the grooveat the top end of the spacer 210 but flows downwardly on the lateralside of the alignment film 109. Accordingly, the alignment film 109 isnot formed thick in the concave portion 212.

The width of the concave portion at the top end of the columnar spacer210 is increased in the central portion, and the pedestal 120 on the TFTsubstrate 100 intrudes to this portion. Although the pedestal 120 issquare in a plan view, the planar shape is not restricted only theretobut may be circular, rectangular, or elliptic. The planar shape isdetermined depending on the shape of the pedestal base 130.

Since the alignment film 109 is not formed thick in the concave portion212 of the columnar spacer 210, scraping of the alignment film does notresult in a serious problem. In addition, as shown in FIG. 2 and FIG. 3,since the pedestal 120 is surrounded by the convex portion 211 of thecolumnar spacer 210, even when the counter substrate 200 is pressed fromthe outside, the columnar spacer 210 does not move easily to thepedestal. Also in this regard, scraping of the alignment film can beprevented. Further, no positional displacement is caused between the TFTsubstrate 100 and the counter substrate 200.

In FIG. 2, when the counter substrate 200 is pressed, the pedestal 120or the columnar spacer 210 is compressed. In this case, when the convexportion 211 of the columnar spacer 210 is in contact with the facingsurface of the TFT substrate 100, reaction is generated therein todisperse the force. Accordingly, the pedestal 120, etc. are notfractured. Further, since the reaction increases gradually, the countersubstrate 200 can recover the initial state in a short time afterremoval of the pressure exerted on the counter substrate 200. Such aneffect can be obtained effectively by defining the distance between theconvex portion 211 of the columnar spacer 210 and the facing surface ofthe TFT substrate 100 to 0.2 μm or more.

FIG. 4 shows another example of this embodiment. The embodiments in FIG.4 and FIG. 2 are different in that the depth of the concave portion 212at the top end of the columnar spacer 210 in FIG. 4 is larger than thatin FIG. 2 and the convex portion 211 of the columnar spacer 210 is incontact with the facing surface of the TFT substrate 100 in a usualstate and the pedestal 120 is not in contact with the concave portion212 of the columnar spacer 210 in the usual state. The plan view showinga relation between the columnar spacer 210 and the pedestal 120 in thepedestal portion is identical with FIG. 3.

The configuration can be obtained by increasing the depth of the concaveportion 212 of the columnar spacer 210, and, in addition, by loweringthe height of the pedestal 120. The height of the pedestal 120 can beadjusted depending on the height of the pedestal base 130 formed below.The height can be adjusted by removing the semiconductor layer 103, thedrain electrode layer 104, or the pixel electrode 106 from the pedestalbase 130.

In the embodiment in FIG. 4, when a force is exerted on the countersubstrate 200, the convex portion 211 of the columnar spacer 210 iscompressed at first. When the force on the counter substrate 200 furtherincreases, the pedestal 120 is in contact with the concave portion 212of the columnar spacer 210. This increases the reaction. By the effectas described above, the columnar spacer 210 or the pedestal 120 can befree from fracture and the counter substrate 200 can recover the initialstate in a short time after removal of the pressing force therefrom inthe same manner as the configuration of FIG. 2. In FIG. 4, the distancebetween the top end of the pedestal 120 and the concave portion 212 ofthe columnar spacer 210 is preferably 0.2 μm or more.

FIG. 5 is a plan view showing a further example of this embodiment.While the columnar spacer 210 in FIG. 2 and FIG. 4 is a truncated conehaving a circular shape in a plan view as shown in FIG. 3, the spacer inFIG. 5 is a truncated pyramidal cone having a square shape in a planview. The top end of the columnar spacer 210 in FIG. 5 is square, andconvex portions 211 are formed each at the corners of the square shape.The concave portion 212 is formed in a grooved shape from the centralportion where the pedestal 120 intrudes to each of the sides and thegroove is opened to the lateral side of the columnar spacer 210.

Since the liquid material of the light alignment film flows from thegrooved portion formed at the top end of the columnar spacer 210 to thelateral side of the columnar spacer 210, the alignment film 109 is notformed thick in the concave portion 212. Accordingly, scraping of thealignment film caused by contact between the pedestal 120 and thecolumnar spacer 210 can be prevented. Further, since the pedestal 120 issurrounded by the convex portion 211 of the columnar spacer 210, theproblem of positional displacement between the counter substrate 200 andthe TFT substrate 100 does not occur.

Also in the case where the columnar spacer 210 and the pedestal 120 havea planar shape as shown in FIG. 5, the cross sectional shape of thecolumnar spacer 210 and the pedestal 120 can be in the sameconfiguration as in FIG. 2 or FIG. 4. Accordingly, when the countersubstrate 200 is pressed from the outer side, the columnar spacer 210 orthe pedestal 120 can be free from fracture and the recovery time to theinitial state upon removal of pressure on the counter substrate 200 canalso be shortened.

Second Embodiment

FIGS. 6 to 8 are views showing the shape and the arrangement of thecolumnar spacers 210 according to a second embodiment of the invention.FIG. 6 and FIG. 7 are plan views showing the state where the pedestal120 intrudes to the concave portion 212 of the columnar spacer 210.

FIG. 6 shows a state in which a groove-shaped concave portion 212 openedat the ends thereof in the longitudinal direction, that is, in a ydirection is formed on the top end of the columnar spacer 210. FIG. 7shows a state in which a groove-shaped concave portion 212 opened at theends thereof in the lateral direction, that is, in an x direction isformed on the top end of the columnar spacer 210.

In both of the columnar spacer 210 in FIG. 6 and the columnar spacer 210in FIG. 7, since the concave portion 212 is opened at the ends and theliquid alignment film flows to the outside, the alignment film 190 isnot formed thick in the concave portion 212. Accordingly, scraping ofthe alignment film can be prevented.

In FIG. 6, the pedestal 120 cannot move in the lateral direction, thatis, in the x direction due to the presence of the convex portion 211 ofthe columnar spacer 210. That is, lateral displacement between thecounter substrate 200 and the TFT substrate 100 can be prevented. InFIG. 7, the pedestal 120 cannot move in the longitudinal direction, thatis, in the y direction due to the presence of the convex portion 211 ofthe columnar spacer 210. That is, longitudinal displacement between thecounter substrate 200 and the TFT substrate 100 can be prevented.

Accordingly, displacement between the TFT substrate 100 and the countersubstrate 200 can be suppressed in both of the x direction and the ydirection by the combination of the columnar spacer 210 in FIG. 6 andthe columnar spacer 210 in FIG. 7. FIG. 8 is an example in which sucheffects can be obtained by the combination of the columnar spacer 210shown in FIG. 6 and the columnar spacer 210 shown in FIG. 7.

In FIG. 8, each of blank circles represents the columnar spacer 210 asshown in FIG. 6 and each of hatched circles represents the columnarspacer 210 as shown in FIG. 7. In FIG. 8, positional displacementbetween the TFT substrate 100 and the counter substrate 200 in both ofthe x direction and the y direction is prevented by alternatelyarranging the columnar spacers 210 shown in FIG. 6 and the columnarspacers 210 shown in FIG. 7.

Incidentally, when the counter substrate 200 of the liquid crystaldisplay panel is pressed by a finger, an identical stress is not appliedto all of the regions in a display region 400. For example, when acentral portion of the display region 400 is pressed shown in FIG. 9C, astress in the y direction is applied in a region A near the longer sideof the display region 400, and a stress in the x direction is applied inthe region B near the shorter side. For preventing the positionaldisplacement by the stresses, in the region A of FIG. 9C, displacementin the y direction can be prevented by using more number of the columnarspacers 210 shown in FIG. 9A where the groove at the top end of thecolumnar spacer 210 is formed in the x direction. Displacement in the xdirection can be prevented by using more number of columnar spacers 210in the region B of FIG. 9C where the groove at the top end of thecolumnar spacer 210 is formed in the y direction.

FIG. 10 and FIG. 11 are plan views for the combination of the columnarspacer 210 and the pedestal 120 showing other examples of thisembodiment. FIG. 10 shows an example where convex portions 211 areformed by the number of three each at 120° interval in view of polarcoordination at the top end of the columnar spacer 210. Then, concaveportions 212 each opened at the end are formed by the number of three. Apedestal 120 intrudes to the concave portion 212 of each of the regionspartitioned by the three convex portions 211.

In FIG. 11, three convex portions 211 formed at the top end of thecolumnar spacer 210 are disposed each to a position rotated by 60 degreewhen compared with FIG. 10. Other shapes are identical with those inFIG. 10. By the combined use of the columnar spacer 210 shown in FIG. 10and the columnar spacer 210 shown in FIG. 11, the configuration can beattained in which the displacement is suppressed in any of the xdirection and the y direction of a display region 400 shown at FIG. 9C.

FIG. 10 and FIG. 11 are in such a relation that the convex portions 211at the top end of the columnar spacer 210 are rotated each by 60 degree.In this case, when the number of the convex portions 211 formed at thetop end of the columnar spacer 210 is defined as 3, the rotational angleof the convex portions 211 can be calculated as 360/(3×2). The number ofthe convex portions 211 at the top end of the columnar spacer 210 canalso be the number of n which is 4 or greater. In this case, a liquidcrystal display panel with less displacement between the countersubstrate 200 and the TFT substrate 100 can be attained by defining thepositions of the convex portions 211 in the two types of the columnarspacers 210 in such a relation that they are rotated by 360/(n×2) andarranging the two kinds of the columnar spacers 210 in combination.

Third Embodiment

FIG. 12 is a cross sectional view showing a relation between a columnarspacer 210 and a pedestal 120. FIG. 13 is a plan view of a combinationof the columnar spacer 210 and the pedestal 120 as viewed on the side ofthe TFT substrate 100. As shown in FIG. 12 and FIG. 13, a convex portion211 and a concave portion 212 are formed each by one on the top end ofthe columnar spacer 210. The concave portion 212 is opened to theoutside except for the side of the convex portion 211 and, accordingly,the material of the alignment film does not form a liquid reservoir.That is, the alignment film 109 is not formed thick in the concaveportion 212.

In FIG. 12, a convex portion 211 and a concave portion 212 are formed atthe top end of a columnar spacer 210. While the convex portion 211 is incontact with the TFT substrate 100, the pedestal 120 formed on the TFTsubstrate 100 is not in contact with the concave portion 212 at the topend of the columnar spacer 210. When an external force is exerted on thecounter substrate 200 of the liquid crystal display panel, the pedestal120 of the TFT substrate 100 and the concave portion 212 of the columnarspacer 210 are in contact with each other to generate larger reaction.Accordingly, the stress to the pressure can be increased gradually, andthe recovery time to the initial state when pressure is removed can beshortened.

In FIG. 14, contrary to FIG. 12, a pedestal 120 formed on the TFTsubstrate 100 is in contact with a concave portion 212 of a columnarspacer 210, but the convex portion 211 of the columnar spacer 210 is notin contact with the TFT substrate 100. When an external force is exertedon the counter substrate 200 of the liquid crystal display panel, theconcave portion 211 of the columnar spacer 210 and the TFT substrate 100are in contact with each other to cause greater reaction. The effect isidentical with that in FIG. 12. The plan view on the side of the TFTsubstrate 100 in FIG. 14 is identical with that of FIG. 13.

In FIG. 12 or FIG. 14, the pedestal 120 constrains the movement of thecolumnar spacer 210 only in one direction. That is, the movement cannotbe restricted in the direction other than the direction where the convexportion 211 is formed at the top end of the columnar spacer 210. In thisembodiment, positional displacement between the TFT substrate 100 andthe counter substrate 200 is prevented as the entire liquid crystaldisplay panel by arranging the columnar spacers 210 in FIG. 12 or FIG.14 while changing the direction thereof.

FIG. 15 is an example of arranging the columnar spacers 210 in thisembodiment. In a plan view for the columnar spacers 210 in FIG. 15, theprotrusion 211 is formed on the left in the spacer A, the protrusion 211is formed on the right in the spacer B, the protrusion 211 is formedabove in the spacer C and the convex portion 211 is formed below in thespacer D. In FIG. 15, pixels partitioned by the gate lines 101 and thedata lines 111 are arranged by the number of 15. The pedestal 120 isformed over the gate line 101 and the columnar spacer 210 is alsoarranged over the gate line 101.

As shown in FIG. 15, spacers A in which the convex portion 211 is formedon the left at the top end of the columnar spacer 210 and spacers B inwhich the convex portion 211 is formed on the right at the top end ofthe columnar spacer 210 are arranged alternately over the uppermost gateline 101. Further, spacers C in which the convex portion 211 is formedabove at the top end of the columnar spacer 210 are arranged over thesecond gate line 101 from above. Spacers A in which the convex portion211 is formed on the left and spacer B in which the convex portion 211is formed on the right are alternately arranged over the third gate line101 from above. In this case, they are arranged while displacing therelation between the spacers A and B each by one row relative to the rowof the pixels from the arrangement over the uppermost gate line 101.Spacers D in which the convex portion 211 is formed below at the top endof the columnar spacer 210 are arranged over the lowermost gate line101.

As described above, in this embodiment, displacement between the TFTsubstrate 100 and the counter substrate 200 is restricted over theentire display region 400. Arrangement for the columnar spacers A, B, C,and D shown in FIG. 15 is illustrated as an example and the relation ofthe number may be changed for the columnar spacers A, B, C, and Ddepending on the place as shown in the example of FIGS. 9A to 9C.

Further, in the plan view of the columnar spacer 210 in FIG. 15, whilethe boundary between the convex portion 211 and the concave portion 212is identical with the extending direction of the data line 111 or thegate line 101, this embodiment is not restricted thereto but theboundary between the convex portion 211 and the concave portion 212 maybe at a predetermined angle relative to the data line 111 or the gateline 101. It is important in four types of the columnar spacers 210 thatthe directions of the boundary lines between the convex portion 211 andthe concave portion 212 are different by 90° from each other.

Fourth Embodiment

FIGS. 16 to 18 are views showing a fourth embodiment of the invention.In the first to third embodiments, the pedestal 120 is formed over thegate line 101. The pedestal 120 is formed by forming the pedestal base130 below, for example, by using the semiconductor layer 103, the drainelectrode layer 104, the pixel electrode layer 106, etc. In thisembodiment, the drain electrode 104 and the source electrode 105 of theTFT are utilized as the pedestal base 130 without additionally formingthe pedestal base 130.

FIG. 16 is a plan view of a pixel in this embodiment. In FIG. 16, a TFTis formed over a gate line 101 and a columnar spacer 210 is arranged tothe portion of the TFT. Other configurations are identical with thoseexplained in FIG. 1.

FIG. 17 is a cross sectional view along line B-B in FIG. 16. In FIG. 17,a gate line 101 is formed over a TFT substrate 100 and a gate insulatingfilm 102 is formed over the gate line 101. A semiconductor layer 103 isformed over the gate insulating film 102, and a drain electrode 104 anda source electrode 105 are disposed over the semiconductor layer 103.The drain electrode 104 and the source electrode 105 also serve as apedestal base 130. An inorganic film 107 is formed so as to cover thedrain electrode 104 and the source electrode 105, and an alignment film109 is formed thereover. The configuration on the side of the countersubstrate 200 is identical as has been described with reference to FIG.2.

A convex portion 211 and a concave portion 212 are formed at the top endof a columnar spacer 210 formed over an overcoat film 203 of a countersubstrate 200. In FIG. 17, a convex portion 211 at the top end of thecolumnar spacer 210 is in contact with the TFT substrate 100. A concaveportion 212 of the columnar spacer 210 is not in contact with a pedestal120 formed on the TFT substrate 100. Then, when pressure is exerted onthe counter substrate 200 of the liquid crystal display panel, theconvex portion 211 at the top end of the columnar spacer 210 iscompressed and the concave portion 212 of the columnar spacer 210 andthe pedestal 120 are in contact with each other.

FIG. 18 is a plan view showing a relation between the drain electrode104 and the source electrode 105 used as the pedestal base 130, and theconvex portion 211 and the concave portion 212 of the columnar spacer210. In FIG. 18, the drain electrode 104 and the source electrode 105formed over the semiconductor layer 103 are arranged corresponding tothe concave portion 212 of the columnar spacer 210. The drain electrode104 and the source electrode 105 are constrained by the convex portion211 formed at the top end of the columnar spacer 210. As a result,positional displacement between the TFT substrate 100 and the countersubstrate 200 in the liquid crystal display panel can be prevented.

In FIG. 18, since the concave portion 212 at the top end of the columnarspacer 210 is opened at the ends, the liquid material of the alignmentfilm does not accumulate in the concave portion. Accordingly, since thealignment film 109 is not formed thick in the concave portion,occurrence of bright spots caused by scraping of the alignment film canbe suppressed. As described above, this embodiment has an advantage thatthe same configuration as in the existent embodiment can be used on theside of the TFT substrate 100 and, accordingly, can be formed by usingthe same mask as in the existent embodiment.

In the configuration of FIG. 17, the top end of the pedestal 120 formedby the drain electrode 104 and the source electrode 105 are not incontact with the concave portion 212 of the columnar spacer 210 in ausual state. Alternatively, by decreasing the height of the convexportion 211 of the columnar spacer 210, it may be configured such thatthe pedestal 120 and the concave portion 212 of the columnar spacer 210are always in contact with each other, and the convex portion 211 of thecolumnar spacer 210 and the TFT substrate 100 are in contact with eachother when a pressure is exerted on the counter substrate 200 in thesame manner as shown in FIG. 2.

Fifth Embodiment

FIGS. 19A and 19B are cross sectional views showing a fifth embodimentof the invention. FIG. 19A is identical with FIG. 17. In FIG. 19B, aconvex portion 211 is not formed on a columnar spacer 210. In FIG. 19B,the columnar spacer 210 is not in contact with a pedestal 120 formed bya drain electrode 104 and a source electrode 105 in a usual state of acolumnar spacer 210, that is, in a state where pressure is not exertedon a counter substrate 200.

Particularly, in this embodiment, when a pressure is exerted on thecounter substrate 200 of the liquid crystal display panel, the stress isdispersed by the combined use of the columnar spacers 210 in FIG. 19Aand in FIG. 19B, and the time to recovery the initial state is shortenedupon pressure is removed. That is, when the pressure is exerted on thecounter substrate 200 of the liquid crystal display panel, the columnarspacer 210 shown in FIG. 19B is at first in contact with the pedestal120 and, when the pressure is further exerted, the concave portion 212of the columnar spacer 210 shown in FIG. 19A is in contact with thepedestal 120. Depending on the gap between the columnar spacer 210 andthe pedestal 120, the order of contact between the spacer and thepedestal may be reversed.

Sixth Embodiment

In the invention, it is essential to form the convex portion 211 and theconcave portion 212 at the top end of the columnar spacer 210.Accordingly, the diameter of the columnar spacer 210 of the inventiontends to be increased. The pedestal 120 and the columnar spacer 210 areoften formed at the portion corresponding to the gate line 101. Althoughthe gate line 101 is formed at a large width, when the diameter islarger as in the columnar spacer 210 of the invention, the columnarspacer may sometimes protrude out of the gate line 101.

In FIG. 20, a columnar spacer 210 is disposed over a gate line 101 and,since the diameter of the columnar spacer 210 is large, the formedcolumnar spacer 210 is formed in a state of protruding from the gateline 101. Other configurations of FIG. 20 are identical with those ofFIG. 1. In a portion where the columnar spacer 210 is formed, alignmentof liquid crystals becomes abnormal to generate domains when rubbingalignment is adopted.

FIG. 22 is a plan view showing a state in which a not rubbed portion isleft at the periphery of a columnar spacer 210 when initial alignment isapplied to the counter substrate 200 by a rubbing treatment, and lightleakage 610 is caused at that portion. In FIG. 22, an arrow shows therubbing direction 600. In FIG. 22, since the columnar spacer 210 has aheight, not rubbed portions are formed at the periphery of the columnarspacer 210 as shown by hatched lines in FIG. 22. The portions causelight leakage 610 to deteriorate the contrast. Accordingly, the portionshave to be shielded against light, for example, by a black matrix 201 orthe like formed on the counter substrate 200. However, transmittance ofthe liquid crystal display panel is deteriorated.

This embodiment intends not to deteriorate the transmittance even whenthe diameter of the columnar spacer 210 is large, by utilizing also thelateral side of the columnar spacer 210 as the display region byadopting the optical alignment together in the invention. In the opticalalignment, a polarized UV light is applied to the alignment film 109thereby causing monoaxial anisotropy and conducting initial alignment ofliquid crystals. Accordingly, since alignment ability can be obtained inthe optical alignment by polarized UV light irradiation, the rubbingshadow 610 which is generated in the rubbing alignment is not caused.

FIG. 21 is a cross sectional view along line C-C in FIG. 20. In FIG. 21,the configuration on the side of a TFT substrate 100 is identical withthat of FIG. 2 or FIG. 4. A black matrix 201 and a color filter 202 areformed on a counter substrate 200 and an overcoat film 203 is formed soas to cover them. A columnar spacer 210 is formed over the overcoat film203. The diameter of the columnar spacer 210 is larger than the width ofthe gate line 101.

In the rubbing alignment, since the rubbing shadow is generated, thewidth of the black matrix 201 is formed larger than the diameter of thecolumnar spacer 210 to prevent deterioration of the contrast. However,in the invention, the width of the black matrix 201 is smaller than thediameter of the columnar spacer 210 as shown in FIG. 21. The diametermeans herein the diameter of the columnar spacer 210 in a trapezoidalcross section for a portion having a larger width, that is, the diameterof a lower bottom 216. Specifically, also the lateral side of thecolumnar spacer 210 is used as the display region 400 as shown by arrows500 that show a transmission light in FIG. 21.

The alignment film 109 is formed also on the lateral side of thecolumnar spacer 210 and by a polarized UV light irradiation to thealignment film 109, alignment ability is provided to liquid crystalmolecules. Since the columnar spacer 210 has a predetermined height, thethickness of the alignment film 109 tends to be decreased on the lateralside of the columnar spacer 210. Also in such a case, the alignment film109 can be formed at such a thickness that can provide optical alignmentup to about ⅔ the height of the columnar spacer 210.

As described above according to this embodiment, since it is notnecessary to enlarge the light shielding region by the black matrix 201also in the configuration where the convex portion 211 and the concaveportion 212 are formed at the top end of the columnar spacer 210 and thediameter of the columnar spacer 210 is increased, degradation of thetransmittance of the liquid crystal display panel can be suppressed.

The invention claimed is:
 1. A display device comprising a transistorsubstrate and a counter substrate opposing to the transistor substrate,wherein the counter substrate comprising a first spacer and a thirdspacer, the transistor substrate comprising a transistor having a drainelectrode, a source electrode and a semiconductor layer, a pixelelectrode electrically connecting the transistor, and a second spacer,and a fourth spacer, the first spacer opposing to the second spacer, thethird spacer opposing to the fourth spacer, the first spacer has a firstsidewall extending in a first direction in a plan view, the secondspacer has a second sidewall extending in the first direction, the firstsidewall and the second sidewall oppose to each other in the plan view,a length of the first sidewall in the first direction is longer than alength of the second sidewall in the first direction, the third spacerhas a third sidewall extending in a second direction in the plan view,the second direction crosses the first direction in the plan view, thefourth spacer has a fourth sidewall extending in the second direction,the third sidewall and the fourth sidewall oppose to each other in theplan view, a length of the third sidewall in the first direction islonger than a length of the fourth sidewall in the first direction. 2.The display device according to claim 1, wherein the second spaceroverlaps with the semiconductor layer, in the plan view.
 3. The displaydevice according to claim 1, wherein a gap exists between the firstspacer and the transistor substrate.
 4. The display device according toclaim 1, wherein the first spacer having a first area opposing to thesecond pacer and a second area not opposing to the second spacer.
 5. Thedisplay device according to claim 1, wherein the first spacer having aconcave portion, the second spacer is in contact with the concaveportion.
 6. The display device according to claim 1, wherein a height ofthe first spacer is bigger than a height of the second spacer.
 7. Thedisplay device according to claim 1, wherein the first substrate furthercomprising a plurality of data lines and a plurality of gate lines, thepixel electrode is formed in a pixel area surrounded by the plurality ofdata lines and the plurality of gate lines, the plurality of the gatelines include a first gate line and a second gate line, wherein thesecond spacer overlaps with the first gate line and the fourth spaceroverlaps with a second gate line.
 8. The display device according toclaim 1, wherein the first gate line and the second gate line areadjacent to each other.
 9. The display device according to claim 1,wherein the second direction crosses the first direction in a rightangle.